American Scientist

What Makes Biology Unique? Ernst Mayr. xiv + 232 pp. Cambridge University Press, 2004. $30.

Evolution is a young theory. As someone who received his Ph.D. in 1975, I have been professionally active for 20 percent of the era that comprises the history of the subject (taking Darwin's Origin as the starting point). Yet I am a newcomer compared with Ernst Mayr, who will celebrate his 101st birthday this year and has been professionally active for more than 50 percent of that history. He has now published his 25th book, What Makes Biology Unique? It is a collection of essays on a wide range of topics, including the nature of biology as a scientific discipline, the problem of defining just what it means to be a species (the subject for which he is perhaps best known), human evolution and the possibility of life elsewhere in the universe.

Mayr has a lean prose style that assumes no special knowledge and gets directly to the point. His acuity would be remarkable at any age. His essays reflect the recent literature as much as can be expected, given their broad scope, but their greatest virtue is their historical and conceptual depth. Not only has Mayr been a major force for much of the history of evolutionary theory, but he is also a philosopher and a scholar of the old school who believes in tracing ideas to their roots. Thus he cites Aristotle and Kant as frequently as the newest discoveries in molecular biology or human origins.

In my experience, contemporary scientists and their students tend to lack historical depth and philosophical curiosity; they could thus benefit greatly from the expansiveness of Mayr's view. His major theme is that the concept of science was originally based on mathematics and physics and that biology does not fit that conception, which has caused many to regard it as "immature" or "soft" in some sense, whereas in reality it is the concept of science that needs to be changed to accommodate differences between biological and physical systems. For example, experiments cannot be conducted on historical claims about evolution, but alternative historical narratives can be constructed and tested against evidence (the same goes for the physical sciences of astronomy and geology). Evolutionary processes are less deterministic and lawlike than are physical processes, but there is still a notion of "concepts" that can be tested experimentally. Above all, everything that evolves has two explanations—proximate and ultimate—only one of which can be reduced to physical processes.

Readers will also benefit from Mayr's long view of the history of biology. He considers revolutionary developments that took place before Darwin, the fact that Darwin's theory is a constellation of what were then fundamentally new (and largely independent) claims, and the many subsequent developments that led to the theory as we know it today.

Mayr's philosophical bent is combined with a pragmatism that can be refreshingly blunt. In the essay "Do Thomas Kuhn's Scientific Revolutions Take Place?," Mayr shows (rather convincingly, given the brevity of the piece) that scientific progress in biology bears little resemblance to the notion of paradigms developed by Kuhn. In "Are We Alone in This Vast Universe?" Mayr regards the origin of life on other planets with suitable conditions as probable, but he considers the likelihood that such life could communicate with us electronically to be vanishingly remote, and he deems the search for it a waste of time and money. He even views efforts to find out whether primitive life evolved elsewhere in the solar system as wrongheaded—arguing, for example, that the money spent looking for hints of life on Mars is exorbitant:

The money could have been spent far more effectively in researching the rapidly dwindling diversity of the tropical rainforests on earth. But that urgent task is neglected in favor of possibly finding some fossil bacteria on Mars. Should we perhaps organize a search for terrestrial intelligence?

It is possible to take issue with Mayr on numerous details. His critique of reductionism is valid in some respects but also takes too literally the familiar holistic adage that "the whole is more than the sum of its parts"—as if reductionists ignore nonadditive interactions. He misrepresents the problem of group selection as one of reductionism versus holism. In the standard model of altruism that evolves by group selection, all the effects are additive. The reason that group selection is required is because the altruistic trait is selectively disadvantageous within groups; to evolve, it requires the ingredients of natural selection at the group level (a population of groups with variation, heritability and fitness differences). However, specific issues such as these do not seriously detract from the main virtue of the book on a broader scale.

Readers who are already familiar with Mayr's contributions to biology and philosophy will find primarily summaries and updates on the same themes, although he is also refreshingly candid about changing his mind on such subjects as the importance of sympatric speciation (the processwhereby evolutionary lines diverge without having been geographically  isolated). What Makes Biology Unique? offers newcomers an entertaining way to expand their horizons. We are lucky that someone who has experienced so much remains forever young in his thinking.—David Sloan Wilson, Biology and Anthropology, Binghamton University, Binghamton, New York